Refinement of the incommensurate structure of high quality Bi-2212 single crystals from a neutron diffraction study

• Published in: Physica. C, Superconductivity Superconductivity, 1998-01, Vol.294 (3), p.275-288
• Main Authors: Miles, P.A, Kennedy, S.J, McIntyre, G.J, Gu, G.D, Russell, G.J, Koshizuka, N
• Format: Article
• Language: English
• Subjects: Bi-2212 crystals; Bi-based cuprates; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cuprates superconductors (high tc and insulating parent compounds); Exact sciences and technology; High-Tc compounds; Incommensaturate crystals; Incommensurate crystals; Incommensurate structure; Neutron diffraction; Physics; Semi-periodic solids; Structure of solids and liquids; crystallography; Superconductivity
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(97)01682-1

We report the results of the refinement of data collected by neutron diffraction from a large single crystal of Bi 2Sr 2CaCu 2O 8+ x (Bi-2212) which has an incommensurately modulated superlattice. These results are important in locating the positions of the oxygen atoms and their modulation by using four-dimensional crystallographic analysis. The four-dimensional space group is found to be consistent with N Bbmb/11̄1. We do not find excess oxygen but do observe large modulations in the oxygen associated with the bismuth ions in the lattice. This is consistent with the superconducting transition temperature of 91 K with a sharp 2 K width obtained from oxygen deficient “as-grown” crystals. Our overall weighted r-factor is 0.052 including up to second order satellites, which is better than other published results for both single crystals and powders, obtained from X-ray and neutron diffraction studies.